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Most Valheim dedicated-server startup failures come from the launch script: an invalid argument, a missing world in the selected save directory, or a script reset by a Steam update. Start by checking the copied launch script and its -name, -world, -password, -port, -public, -savedir and -crossplay values. If the log reaches Game server connected
, the process has started successfully; a server that friends cannot find then needs network or discovery troubleshooting rather than more launch-argument changes.
First, identify which failure you have
Do not treat every symptom as a failed startup. A console window that closes immediately, a world that is replaced by a new one, and a server that starts but is invisible to friends have different causes. Use the symptom table to choose the first check instead of changing several settings at once.
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| What you see | What it usually means | First check |
|---|---|---|
| The window closes immediately | The script exited on an argument, executable-path, permission or file error. | Run the copied script from the installed server directory and enable a persistent log with -logFile. |
| The server creates a fresh world | The requested world name or save directory does not point to the existing files. | Verify -world exactly and inspect the directory selected by -savedir. |
| The console stays open but friends cannot find the server | Startup may be complete; browser discovery, firewall or router configuration is failing. | Look for Game server connected, then check the selected backend and network path. |
The log never reaches Game server connected |
The process has not completed startup. | Read the first error in the log and correct one launch variable at a time. |
What a successful startup looks like
Iron Gate’s official guide states that when the server program displays Game server connected
, the server is up and ready to accept connections. This message is the dividing line for troubleshooting. Errors before it concern the executable, script, arguments, files, permissions or world loading. Problems after it concern reachability, listing and player compatibility.
Leave the console running while testing. Closing it terminates the dedicated-server process unless you are using a service manager or managed host. If you need evidence after a crash or reboot, add -logFile to the launch arguments so output is written to a persistent file. Record the first error, not merely the final shutdown line; later messages often describe consequences rather than the original fault.
Step 1: use the correct dedicated-server tool and preserve your script
Install Valheim Dedicated Server from Steam Tools
In the Steam client, open the Tools section of your library and install Valheim Dedicated Server. This is separate from launching the game client. Open the tool’s installation folder and locate the supplied launcher: start_headless_server.bat on Windows or start_server.sh on Linux.
Copy the supplied launcher before editing
Make a working copy of the original script, then edit the copy. Steam updates can replace or reset the supplied launcher. If a server stopped starting immediately after an update, compare the current original with your saved copy; custom names, worlds, ports and other arguments may have been removed. Keep the copy in the server directory unless you deliberately use absolute paths and understand the permissions involved.
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Launch from the server directory
The executable and its supporting files are expected to be found relative to the installed server directory. A script started from another working directory can fail to locate files even when the installation is intact. Use the copied script as the entry point rather than double-clicking a different executable, and confirm that the script’s executable path still matches the current installation after an update.
Step 2: validate every launch argument
A single malformed value can stop startup. Check the arguments as a set, because changing the port or world while leaving a conflicting value elsewhere can create a new problem that hides the original one.
| Argument | Requirement | Typical failure |
|---|---|---|
-name |
Use a unique server name. Do not include the password in it. | The server is difficult to identify, or password rules reject the combination. |
-world |
Match the existing world name exactly, including spelling and capitalization as stored by the server. | A new world is generated or the existing world cannot be found. |
-password |
Use at least five characters. It must not appear in the server name. | Startup is rejected because the password is too short or exposed in the name. |
-port |
Use a numeric port and keep the router and firewall rules aligned with it. | The process starts on an unexpected port or cannot bind as configured. |
-public |
Use the intended visibility setting consistently with how players should discover the server. | The server is running but does not appear as expected in a browser. |
-savedir |
Point to a directory that the service account can read and write. | Worlds, permission files or logs appear missing, or startup fails on access. |
-crossplay |
Add this flag only when you want the PlayFab relay backend. | You troubleshoot router forwarding even though the relay is intended, or expect Steam-only behavior from crossplay. |
Use a minimal, readable command line
Keep one known-good copy of the script and format its arguments so each value is easy to inspect. A template inside a script might look like this:
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-name "YOUR_SERVER_NAME" -world "YOUR_WORLD_NAME" -password "YOUR_PASSWORD" -port 2456 -public 1 -savedir "YOUR_SAVE_DIRECTORY" -logFile "server.log"Replace the values in the code example with real values; do not include the angle-bracket notation in the command. Add -crossplay only for the relay backend. The executable must be launched from the dedicated-server installation directory, and the account running it must have read/write access to the save directory and log location.
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Check the password rules before testing networking
A password shorter than five characters, or a password embedded in the server name, can prevent a valid-looking command from starting. Choose a unique name and a separate password of five or more characters. Do not use the server name as the password simply to make testing easier; that can violate the same rule you are trying to diagnose.
Step 3: fix world and save-directory mismatches
Understand what -world selects
The -world value is a world name, not a path to a random file. If the value does not match the existing world, the server can behave as though no save exists and create a new world. Check the exact name used when the world was created, then use that name consistently in the script.
Understand what -savedir changes
-savedir changes where the server reads and writes worlds and permission files. Moving this value changes the location the process searches; it does not move or rename existing saves automatically. A correct world name in the wrong save directory still appears to be missing.
Iron Gate documents these default save locations in its 2024 guide:
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- Windows:
%USERPROFILE%/AppData/LocalLow/IronGate/Valheim - Linux:
~/.config/unity3d/IronGate/Valheim
If you previously used a custom directory, inspect that directory first. Confirm that the account running the server can list, read and write the files. A service account may have different permissions from your interactive desktop account, even when both use the same machine.
Recover a world that appears to have vanished
- Stop the server cleanly and make a backup copy of the existing save directory.
- Read the script’s
-savedirvalue and resolve the full path it represents. - Compare the world name in
-worldwith the names of the saves in that directory. - Correct only the path or name that is wrong, then restart with
-logFileenabled. - Confirm the log identifies the intended world before allowing players to make changes.
Do not delete a newly created world until you have verified that the original files are safely copied. Starting the server with a mistaken directory can create a plausible but empty environment, which makes accidental overwrites harder to notice.
Step 4: separate startup from reachability
Once Game server connected
appears, stop changing world and password arguments. The process is running; the remaining question is how players reach it. The answer depends on whether the script uses the default Steam backend or the PlayFab relay selected by -crossplay.
Steam backend: forward two ports
When -crossplay is omitted, the server uses the Steam backend. It uses the configured port and the next port. The documented defaults are 2456–2457 (Iron Gate AB, 2024). If you change -port, forward that selected port and the immediately following port instead of continuing to forward 2456–2457.
- Reserve a stable local IP address for the host computer in the router, or configure an equivalent DHCP reservation.
- Create router port-forwarding rules for the selected port and port+1 to that local IP.
- Allow the dedicated-server executable through the host operating system’s firewall on the required network profiles.
- Restart the server after changing the script or forwarding rules.
- Test from a different network, such as a friend’s connection or a mobile hotspot, rather than relying only on a test from inside the same LAN.
Forwarding only one port can produce a server that appears to start but fails for outside players. A router rule aimed at yesterday’s host IP has the same effect, so verify the destination address after network changes.
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Crossplay backend: use the PlayFab relay
Adding -crossplay switches the server to the PlayFab relay. External players do not require router port forwarding when the relay is used, which makes it useful when you cannot change the router or when direct inbound connections are blocked. It also changes compatibility: a server without the flag uses the Steam backend and is limited to Steam users, while the crossplay backend allows players from supported platforms to connect.
Do not mix the two operating assumptions. If crossplay is enabled, troubleshoot relay availability, the flag’s presence and player-platform support before adding direct forwarding rules. If crossplay is removed, restore the Steam port and firewall checks.
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Capture a persistent log
Add -logFile to the copied launcher. A persistent log survives the brief console window that otherwise disappears and lets you identify the first error after a reboot or update. Keep the log path inside a directory the server account can write to; a protected or nonexistent directory can create a second failure.
Change one variable at a time
Record these values before each test:
- The executable path and working directory
- The complete world name
- The effective
-savedirpath - The selected port and whether
-crossplayis present - Whether
Game server connected
appears
Then make one change, restart, and compare the result. Changing the world, port, password and backend in one attempt prevents the log from telling you which correction mattered. The first error is the useful boundary; messages that follow a failed world load or permission check may simply describe the shutdown.
Interpret common log outcomes
- Failure before world loading: recheck the executable path, argument syntax, password rules and permissions.
- World-not-found behavior: compare
-worldand-savedirwith the actual save location. - Connected message followed by no browser listing: leave the launch settings alone and troubleshoot backend, firewall, forwarding and discovery.
- Different result after a Steam update: compare your working copy with the newly installed original script.
Why an update can make a working server stop starting
The supplied launcher is not a safe place to store custom configuration permanently. Steam updates can reset it, removing your edited name, world, password, port, save directory or log option. The executable may also be installed in a path different from the one referenced by an old script. Keep your copied launcher, and after every update verify that the executable path and argument list still point to the current installation.
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A reset script can explain two apparently unrelated symptoms: the process may fail because required values disappeared, or it may start a default world because the custom -world and -savedir values were lost. Compare files before changing router settings; networking cannot fix a launcher that is no longer selecting the intended save.
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Double-clicking a Windows batch file hides the useful error when the process exits. Run the copied script from a command prompt opened in the server directory, or add -logFile and inspect the resulting file. On Linux, execute the copied shell script from a terminal so permission and path errors remain visible.
- Confirm that the server tool is installed, not merely the game client.
- Confirm that the script references the executable in the current installation directory.
- Check that the chosen
-savedirand log location exist or can be created by the running account. - Validate the password length and name/password separation.
- Check that
-portcontains only a numeric value. - Restore a known-good copied script if an edit introduced the failure.
After each correction, look for Game server connected
. Reaching that state changes the troubleshooting branch to network reachability.
When the server starts but is not visible
A missing browser entry does not prove that the process failed. First confirm the connected message. Then identify the backend from the presence or absence of -crossplay. For Steam, validate both forwarded ports, the host firewall rule and the router’s destination IP. For crossplay, verify that the flag is present and that every player is using a supported platform for the relay.
Discovery and direct connection are separate concerns. A server can be reachable while a browser listing is delayed or filtered. Test with the intended in-game method and with a player outside the host’s local network. If outside access fails only on Steam, inspect forwarding and firewall rules before touching the world files. If crossplay works for some players but not others, check platform support and that everyone is joining through the crossplay backend rather than expecting a Steam-only listing.
Home hosting versus managed hosting
Self-hosting gives you direct control over the script, world files, save directory, firewall and update timing. It also makes you responsible for keeping the process online, applying updates, preserving backups, and correcting router or permission problems. A managed Valheim host can be reasonable when no one in the group can maintain a home server process, but it transfers operational decisions to the provider.
| Decision axis | Home hosting | Managed hosting |
|---|---|---|
| Platform compatibility | You choose Steam or crossplay and maintain the corresponding settings. | Confirm the provider currently supports the backend and player platforms you need. |
| Router requirements | Steam hosting normally requires forwarding the selected port and port+1; crossplay uses the relay. | External routing is usually handled by the provider, but verify how crossplay is implemented. |
| File control | Full access to scripts, worlds, permission files, logs and custom save paths. | Access depends on the provider’s control panel, file tools and export policy. |
| Updates and backups | You schedule updates and protect saves yourself. | Check who performs updates, the backup frequency, retention and restoration process. |
Before paying for a managed service, verify current Valheim support, crossplay support, backup policy, save-file access and program terms. A host that cannot export your world or restore a known-good backup does not remove the risk that caused the original outage; it only moves the risk to a different operator.
Plan backups before changing a broken installation
Copy the entire save directory before changing -world, -savedir or server versions. Iron Gate’s 2024 guide lists a default save interval of 1,800 seconds (30 minutes), a default short-backup interval of 7,200 seconds (2 hours), and a default long-backup interval of 43,200 seconds (12 hours). These are server defaults, not a substitute for an independent copy. A backup made after a mistaken launch can preserve the wrong state, so retain a pre-change copy with a clear date and time.
Quick Recap
- Stop the process before copying live save files when possible.
- Keep at least one copy outside the active save directory.
- Test that a backup contains the expected world name before deleting any apparently new world.
- Document whether the backup came from the default path or a custom
-savedir.
A complete recovery sequence
- Install or verify Valheim Dedicated Server in Steam’s Tools library.
- Copy
start_headless_server.batorstart_server.shand work only on the copy. - Open the script from the server’s installation directory.
- Set a unique
-name, an exact-world, a password of at least five characters, a numeric-port, the intended-publicvalue and a writable-savedir. - Add
-logFileand remove accidental duplicate or conflicting arguments. - Decide whether the Steam backend or
-crossplayrelay matches the players and network available. - Start the server and read the log until it either reports the first error or displays
Game server connected
. - If it fails before connected, correct one script, file or permission issue at a time.
- If it reaches connected, configure Steam forwarding for the selected port and port+1, or test the crossplay relay without router forwarding.
- Have an outside player test, then preserve the working script and a backup of the world.
Final checks before inviting players
- The working script is a copy, not the Steam-supplied original that updates may reset.
- The world name and save directory point to the intended files.
- The server account can read and write saves, permission files and logs.
- The password meets the five-character minimum and is not contained in the server name.
- The selected port is numeric and matches the Steam forwarding rules when the Steam backend is used.
- Both the host firewall and router rules have been checked for the current host IP.
- The log reaches
Game server connected
. - A dated backup exists before players make new progress.
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